Pressure sores or ringworm or else?

Hi! I've discovered bald scaly patches on my dog's "elbows". They are presents on one of the front AND one of the rear legs. (So 2 bald patches total.) Do you think these are mostly pressure sores or I should immediately contact my vet?? Thanks for your help,   First and second photos are the rear leg and the third one is the front leg.

Hello - and thank you for this great question, well illustrated.  If these are Ring-worm, I would reccommend contacting your vet. Also please have a read about keeping yourself and your family safe in this event as anyone, but immunocompromised people in particular, can catch it.  If they are demodex mites, I would reccommend contacting your vet.  If they have come about as a result of excess hairloss (eg hypothyroidism) ditto (although this is not the typical appearance) - and if they have come about as a result of pressure, then ditto as this would likely be associated with arthritic pain.  So, while it's hard to differentiate between all the possible causes from these photos, most of the possibilities would benefit from seeing a vet.  Certain insect bites, possibly less so.  But in balance, seeing your vet would be a good idea.